unesdoc.unesco.orgunesdoc.unesco.org/images/0022/002281/228110e.pdf · CEHI also wishes to thank the individuals and Water Utility companies, desalination companies and private operators

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Caribbean Environmental Health Institute�

THE USE OF DESALINATION PLANTS IN THE CARIBBEAN - 2006 2

Publicado en el 2006 por el Programa Hidrológico Internacional (PHI) de la Oficina Regional de Ciencia para América Latina y el Caribe de la Organización de las Naciones Unidas para la Educación, la Ciencia y la Cultura (UNESCO). Dr. Luis P. Piera 1992, 2º piso, 11200 Montevideo, Uruguay Documento Técnico del PHI-LAC, Nº 5 ISBN 92-9089-093-2 © UNESCO 2006 Las denominaciones que se emplean en esta publicación y la presentación de los datos que en ella figura no suponen por parte de la UNESCO la adopción de postura alguna en lo que se refiere al estatuto jurídico de los países, territorios, ciudades o zonas, o de sus autoridades, no en cuanto a sus fronteras o límites. Las ideas y opiniones expresadas en esta publicación son las de los autores y no representan, necesariamente, el punto de vista de la UNESCO. Se autoriza la reproducción, a condición de que la fuente se mencione en forma apropiada, y se envíe copia a la dirección abajo citada. Este documento debe citarse como:

UNESCO, 2006. The use of desalination plants in the Caribbean. Caribbean Environmental Health Institute. Documentos Técnicos del PHI-LAC, N° 5

Dentro del límite de la disponibilidad, copias gratuitas de esta publicación pueden ser solicitadas a:

PHI-LAC Oficina Regional de Ciencias para América Latina y el Caribe Unesco Montevideo Dr. Luis P. Piera 1992, 2º piso 11200 Montevideo, Uruguay Tel.: + 598 2 413 20 75 Fax: + 598 2 413 20 94 E-mail: [email protected] http://www.unesco.org.uy/phi

mailto:[email protected]

http://www.unesco.org.uy/phi


Table of Contents �

�� Foreword .......................................................................................................... 5 �� Acknowledgments ............................................................................................ 6 �� Executive Summary.......................................................................................... 7 �� Introduction....................................................................................................... 9 �� Background on CEHI........................................................................................ 10 �� Methodology ..................................................................................................... 11 �� Preamble .......................................................................................................... 12 �� Country Situation .............................................................................................. 13

• Antigua and Barbuda ............................................................................ 13 • Bahamas............................................................................................... 15 • Barbados .............................................................................................. 19 • British Virgin Islands ............................................................................. 22 • Trinidad and Tobago............................................................................. 23 • St. Lucia................................................................................................ 27 • Grenada................................................................................................ 29 • Mexico .................................................................................................. 32

�� Conclusions ...................................................................................................... 35 • Why Desalination.................................................................................. 35 • Types .................................................................................................... 35 • Challenges............................................................................................ 35 • Opportunities ........................................................................................ 36 • Legal and Regulatory Overlay .............................................................. 36 • Socio-Economic and Environmental Setting......................................... 36 • Future Potential .................................................................................... 36

�� Recommendations............................................................................................ 38 �� Sources of Information ..................................................................................... 40 �� References ....................................................................................................... 41 �� Acronyms & Technical Abbreviations ............................................................... 42 �� Appendices....................................................................................................... 43

Appendix 1 Desalination by Reverse Osmosis System Appendix 2 Desalination by Multi-Stage Flash Distillation Appendix 3 Multi Effect Distillation (MED) Appendix 4 Vapor Compression Distillation (VCD)��

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Foreword

The increase in the demand of water resources in small island states, mostly due to tourism, has forced both the government and the private sector of small island states to search for new ways of augmenting the volume of fresh water available. Among the different technologies used to obtain fresh water, desalination is rapidly gaining popularity. Consequently, there is a need to improve the existing knowledge in the region in relation to the design, installation and operation of desalination plants. At the UNESCO International Hydrological Programme for Latin America and the Caribbean (IHP-LAC) V Meeting (Kingston, Jamaica, 17-19 March 2004), the IHP National Committee Presidents and Focal Points stated their interest for the Programme to address the thematic of desalination in the near future. Subsequently, at the IHP-LAC V meeting held in Montego Bay, Jamaica, October 9-14, 2005, the participants approved resolution IHP-LAC VI-8 in relation to the establishment of a Working Group on Desalination. Following up on this resolution, the Greater Caribbean Member States and Chile were asked to nominate an expert from their country to the Working Group on Desalination. Six countries nominated a group member, namely: Bahamas, Grenada, Saint Lucia, Mexico, United States of America, Jamaica. UNESCO IHP-LAC contracted CEHI (Caribbean Environmental Health Institute) to carry out a study on the state of desalination in the Caribbean.

The Working Group on Desalination met for the first time in Castries, Saint Lucia, April 10-11, 2006. The event was orgnized by the UNESCO IHP-LAC in collaboration with CEHI and the UNESCO Office in Jamaica. The meeting was attended by representatives of 5 Greater Caribbean Member States and two organizations, namely CEHI and CWWA (Caribbean Water and Wastewater Association). The participants reviewed the state of desalination technological advances and trends in the Greater Caribbean. Following up the exchange of information and discussion on potential future activities, the participants agreed to reafirm the conformation of the Working Group on Desalination as part of UNESCO-IHP LAC groups of experts, and to develop a document on guidelines on desalination for Member States. In addition, it was agreed to carry out an inventory on existing desalination plants in the Caribbean and to further exchange knowledge and expertise on desalination techniques and derived social and economic issues. The members of the group provided additional information that was added to the document prepared by CEHI. The present document is the result of this exercise��

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Acknowledgements The Caribbean Environmental Health Institute would like to acknowledge the United Nations Educational, Scientific and Cultural Organization (UNESCO) for their vision in recognizing the need to address desalination as it contributions to and impacts on the countries of the region, and its scope for further development in the area of desalination. CEHI also wishes to thank the individuals and Water Utility companies, desalination companies and private operators of desalination plants, which contributed to this study including: Antigua and Barbuda - John Bradshaw, Water Manager, Antigua Public Utilities Authority; Daniel Aburime, Production Engineer, Crabbs Power and Desalination Plant, APUA; Rodney Dickenson, Plant Manager, Enerserve/Veolia Water, Crabbs; Thierry Le Cras, Enerserve/Veolia Water, Crabbs Bahamas - Dr. Richard Cant, Assistant General Manager, Water and Sewerage Corporation

Barbados - Dr. John Bwalya Mwansa, Project Manager, Barbados Water Resources Management and Water Loss Studies, Barbados Water Authority; O. Carlyle Bourne, International Hydrological Programme Focal Point, Ministry of Agriculture; Harriet Waldron, Ionics/GE British Virgin Islands – Julian Willock, Ag. Director, Water and Sewerage Department, Ministry of Communications and Works, Government of the British Virgin Islands Trinidad and Tobago - John Thompson, The Desalination Company of Trinidad and Tobago (Desalcott), Point Lisas; Claire McEwan, Desalcott, Point Lisas; Sharon Taylor, Deputy General Manager, Water, Water and Sewerage Authority St. Lucia - Shanta King, Operations Manager, Water and Sewerage Company (WASCO) Grenada- Lester Arnold, Operations Manager, NAWASA; Alphonsus Daniel, Consultant, Daniel and Daniel Consulting, Grenada


Executive Summary Prior to the use of desalination technologies in the Caribbean, water sources were limited largely to treatment and distribution of surface water, spring water, and ground water from aquifers, boreholes and wells. Rainwater harvesting was also practiced where rainfall availability allowed for its exploitation and where none of these were possible, water had to be barged in by boat. The technologies observed for desalination were that of Reverse Osmosis (RO) and Multi-Stage Flash Distillation (MSFD). The RO plants were overwhelmingly more popular. The few MSFD plants appeared to have been older so that the assumption is that RO plants are replacing them, although in Antigua, one of the MSFD plants is also used in electricity generation, and there appears to be opportunities for energy recovery. It is uncertain whether that and there were only a few MSFD plants, which appeared to be older. Some of the advantages to the RO plants was the fact that they occupied less space and represented simpler technology so they easier to operate. In conducting the research for this study, it was found that countries can roughly be categorized as those that are naturally water scarce as a result of geography and those that face an emergent problem of increased water demand or reduced water supply or quality. The water scarce countries have better established national policies, whether written or not as regards water augmentation and desalination in particular. There appears to be no pattern regarding the pricing of water. Whereas in the Bahamas and Barbados, water is reflective of the cost of production, in counties such as the British Virgin Islands (BVI) and Grenada it is heavily subsidized. The standard of living in the BVI is such that this has less of an impact than in Grenada, where the cost is a serious burden to the National Water and Sewerage Authority (NAWASA). Traditionally, Grenada, like St. Lucia and other volcanic islands with significant enough forest cover and water catchment areas for surface and spring water, the cost of water has been relatively low because they have been subsidized by their governments. In the case of St. Lucia however, desalination is largely limited to private resorts and as such there is no direct impact to the national budget or the Water and Sewerage Corporation (WASCO). In Grenada, the reverse osmosis plants were purchased by the government and handed over to NAWASA. Two of the three plants thus acquired have been commissioned and have both been fraught with operational difficulties. The fact that they have been left inactive for up to several months at a time serves to indicate that they are not viewed critical to addressing the water demand issues. The more water scarce countries of the Bahamas and the BVI see desalination as their only viable source of water and as such their policies and supporting actions embrace desalination efforts more firmly. Desalination in Trinidad and Tobago is a response to the growing need for water, particularly the industrial users at the Point Lisas Industrial Estate. What is not used by the industries at Point Lisas is distributed in the mains to feed the domestic supply. This is charged according to the tariff structure for those users, which is much lower than what is charged to industrial users. The public is generally accepting of desalinated water. In the Bahamas, it is actually preferable, with a recorded increase in usage where desalinated water is substituted for groundwater. In Barbados, the desalinated water is mixed in storage with treated groundwater and there was initially a negative public reaction to the taste, but complaints decreased with public education. In Grenada, however, there was and still is a negative reaction to desalinated water with persons preferring to harvest rainwater for consumption, and to use desalinated water for other activities in times of water stress. It was found that there was generally little public education and awareness in the islands or Petit Martinique and Carriacou where the desalinated plants have been operational. There


are also other complications related to the general absence of a distribution network on those islands and the fact that on these two water scarce islands, rainwater harvesting is extensively practiced for which there is no monthly cost. It is extremely difficult for the National Water and Sewerage Authority (NAWASA) to get a market for desalinated water that is generally not trusted and which would require not just purchase but also transportation by the purchaser. In the case of Grenada, it is evident that the government’s policy was not well communicated to all stakeholders, including NAWASA. Even in countries where desalination had a longer history, there was little by way of legislation that addresses desalination specifically. Legislation generally recognized the authority of the water utility to proenduce potable water to satisfy current demand and to explore and pursue viable water augmentation options for future conditions and needs. Where desalination is concerned, because of the cost, several factors have to be addressed. In Trinidad, because of the size of the plant proposed at Point Lisas, the Town and Country Planning Division required a full Environmental Impact Assessment (EIA). Recently in St. Lucia, such proposals from private entities have been referred to the Development Control Authority (DCA) in the Ministry of Physical Planning, Housing and the Environment, who would then seek expert review from CEHI, WASCO and possibly the Fisheries Division. The environmental impacts have so far been determined by all countries studied to be negligible. In Trinidad, because of the size of the plant, there were concerns over the impact of silt on the receiving body as a result of the volume of brine discharged. This was addressed however, with the removal of this silt from the filtrate to a local sanitary landfill. The treated brine is not hazardous and can be safely disposed of in the sea where there is sufficient currents to facilitate rapid dispersion over a short distance. Thus there should be little impact to marine, coastal and benthic ecosystems. Countries utilizing desalination as a water augmentation option do so because it has been judged to offer the quality, quantity or reliability that other sources cannot offer as efficiently. Because of the reliance on energy, desalination may not be as cost effective as other alternatives, but the perceived advantages for each local situation where it has been implemented, has been determined to outweigh the cost. In various countries, the advantages range from the reliability of this option, the characteristic design-own-operate contractual approach that reduces the hassle of managing some of the other more traditional options. The relatively short timeframe in which a reverse osmosis plant can be erected and operationalized can also be a factor. A properly functioning desalination plant produces high quality water that is suitable for a wide range of functions including many industrial applications that require water that exceeds the widely used WHO drinking water guidelines. Going forward, it is strongly recommended that governments adopt a structured approach to the implementation of desalination. This should also be considered for countries that have not implemented desalination plants, as trends throughout the islands suggest that such a move is imminent. The governments should develop a policy and then take the steps to support this with clearly defined steps and procedures. In some of the countries, it is clear that desalination is being implemented in an ad hoc manner and although it is not likely that this will have adverse impacts on human health and safety, (provided the plants are operating optimally), there can be negative environmental impacts if adequate measures are not put in place to safeguard ecological resources. All stakeholders, particularly the regulatory agencies should be consulted in the development of national policies. Additionally, these policies should be developed within the national framework for the management of water, so that it complements other programmes addressing this issue.


Introduction

The Caribbean Environmental Health Institute (CEHI) was contracted by the United Nations Educational, Scientific and Cultural Organization (UNESCO), through the office of the Regional Hydrologist for Latin America and the Caribbean, to develop a study to evaluate the use of desalination plants in the Caribbean, within the context of the water scenario in the region. The study is to identify trends and propose potential developments that include:

• Definition of the potential for desalination in the Caribbean • Identification of the challenges and opportunities of this water supply system • Analysis of the legal and regulatory overlay in the region in relation to desalination • Analysis of the economic and environmental settings and requirements as well as

the societal implications of present and future desalination endeavours • Identification of present trends • Proposal of potential desalination systems development in the region

This report constitutes a summary of work undertaken as of November 14, 2005 on the Study to Evaluate the Use of Desalination Plants in the Caribbean to augment the potable water supply. The scope of the study is intended to cover Caribbean island states that employ desalination as a water augmentation or primary source of potable water, and will also indicate work planned and outputs to be delivered. Further the discussion carried out within the context of the UNESCO /IHP Working Group on Desalination provided additional information which was added to the original base document.


Background on CEHI CEHI has worked in the water sector since its inception and has, as such, developed a wealth of knowledge and expertise on many water management issues and water-related areas in the Caribbean. Current staff has close to 80 years of collective experience in the sector which is one of the core areas of focus as mandated by the Member States through the Board of Directors, which comprises the Ministers of Health of 16 regional countries. In addition, CEHI’s professionals are supported by post-graduate engineering interns, who have contributed their theoretical knowledge and practical training towards this and other projects that address water and water related issues. CEHI has been involved in the past in water supply augmentation initiatives, including desalination and most recently rain water harvesting. Through participation in the Rainwater Partnership, for example, CEHI has led the region in looking at alternative approaches to the traditional surface and groundwater abstraction approaches to water supply.


Methodology

The approach used was that of conducting a literature review, telephone surveys, in-person interviews (where possible) and site visits. Data was obtained from Water Utility Companies in the form of reports, through interviews with technical and administrative personnel, and from private desalination companies operating within the countries of: Antigua and Barbuda, the Bahamas, Barbados, the British Virgin Islands, St. Lucia and Trinidad & Tobago. Information was also sourced from other regional organisations, presentations made by resource persons in the area of water resources management; and from the internet. The information presented reflects a combination of recorded information and anecdotal data. Further details were also sourced through the Caribbean Water & Wastewater Association and the International Desalination Association, among others. Much of the information was obtained electronically, but most was obtained from a combination of hard copy sources, telephone interviews and site visits. Several officers were active in the data gathering and site visits as determined by the available budget and utilizing their presence in the countries targeted. Site visits are conducted in Antigua, Trinidad, Grenada, St. Lucia and Barbados. Review, discussion, and extension of the base document at the St. Lucia Working Group on Desalination meeting (Castries, April 10-11, 2006).


Preamble Desalination is utilized in many islands of the Caribbean. Some of those most noteworthy because of their history with desalination, or because of the significance of their operation, include: Antigua and Barbuda, the Bahamas, Barbados, the British Virgin Islands and Trinidad and Tobago. Interestingly, some of the volcanic islands with surface water sources have recently adopted desalination to meet increased potable water demand created by development objectives and reduced supply due to poor storage, or land use conflicts in watershed areas. In St. Lucia for instance, desalination is utilized by and being planned for some of the larger resorts either in areas where the distribution system does not extend, or in order to satisfy upward fluctuations in demand. There is also the popularly held suspicion that in some countries, desalination is sometimes employed in an attempt to compensate for the losses perpetuated by poor maintenance of the distribution system as it relates to leak detection. The preferred desalination technology option employed in the Caribbean appears to be overwhelmingly that of Reverse Osmosis (RO) (see Appendix 1), although some Multi-Stage Flash Distillation (MSFD) (see Appendix 2) systems are in use in Antigua, the Bahamas and the BVI. Initial concerns with the specificity and technical expertise required to operate and manage this technology has been overcome with the tendency of plants to be operated by private entities, with exclusive long term contracts to sell water to the government or contracting industry. More recently, the RO technology has become less complicated and therefore easier to operate, according to some operators. Some of the advantages of RO include the fact that the plant can be erected and operationalized within a year, and takes up relatively less physical space as compared to distillation plants; and it uses comparatively less energy than other traditional thermal desalination technologies such as MSFD, Multiple Effect Distillation (MED) (see Appendix 3)and Vapor Compression Distillation (VCD) (see Appendix 4). The disadvantage includes the fact that this process, like distillation, is energy dependent and relatively expensive compared to conventional water production from ground and surface water sources. Some countries have utilized dual purpose desalination systems that derive energy from another process, normally power generation. This is particularly true of the larger systems, utilizing thermal technology. Notably in Antigua, the Bahamas, and the BVI, dual systems exist. The thermal energy recovered from power generation is used usually for the MSFD process; or a combination of MSFD and VCD. Reverse Osmosis plants can be designed to use brackish water or seawater. As it requires less energy to produce potable water from brackish water, given the lower levels of salinity, there would be an advantage to using this source. However, the sustainability of brackish water sources can be uncertain whereas seawater is inexhaustible by comparison. Conversion from the use of brackish water to seawater would mean an increase in the cost of production, and would necessitate replacement of the membranes and pumps used, which in itself could amount to the cost of building a new plant (according to Dr. John Bwalya Mwansa, Project Manager, Barbados Water Resources Management and Water Loss Studies, Barbados Water Authority). The technology is improving and it is expected that the efficiency and cost of desalination by RO and probably other desalination technologies will support its continued application in the Caribbean.


Country Situation� The following information has been obtained for the countries indicated, using the methodology described above. Antigua and Barbuda: Antigua and Barbuda is geographically located at 17º 03 North, 61º 48 West and forms part of the Leeward Island group in the Northern Caribbean Sea. The total land area of Antigua and Barbuda approximates 442 km2 with a population of about 78,580 (2003). The country enjoys a relatively consistent tropical maritime climate. While geologically, Barbuda is of limestone origin, Antigua manifests the characteristically mountainous volcanic topography in the south of the island, but a flatter limestone topography in the north. The central plain is a combination of the two geographic formations. Antigua and Barbuda have no significant surface water and they are prone to periodic droughts. Rainfall appears to fluctuate within a seven-year cycle. According 2001 statistics the average annual rainfall for Antigua is 1041 mm (40.98 inches). The municipal water reservoirs have a total storage capacity of about 4,976,480 m3, according to the Ministry of Trade and Planning. The average annual rainfall for Barbuda was given as 882 mm (34.74 inches). Currently, to cope with this, the Development Control Authority stipulates that buildings must be constructed with rooftop rainwater catchments and storage. The use of groundwater has been explored, but it has been determined that it is not available in sufficient quantities for potable water usage. Given the limited land space available for surface catchments, desalination was selected by the Government as a viable method for producing potable water, because of easy access to the beach for feed water, and also because of the relatively cheap electricity rates which existed at the time (i.e. in the late 1980s). The electricity cost for desalination is subsidized by the Government, while the administrative costs are subsidized by the telephone utility. This arrangement is possible because the water, telephone and electric utilities are housed in one umbrella organization, the Antigua Public Utilities Authority (APUA). According to the APUA, whereas EC$23 (US$8.50) per 1000 gallons is paid for water, the actual production cost in Antigua, for APUA, is EC $30 (US$11) per 1000 gallons, without the subsidies. Figures quoted from the Ministry of Planning, appearing in an OAS report on Drought Hazard Assessment and Mapping for Antigua and Barbuda, Post-Georges Disaster Mitigation Project in Antigua & Barbuda and St. Kitts & Nevis 2001 suggested the following comparison of costs for the production of water from different sources:

Comparative Costs of Water Production from Various Sources

Water Source Production Cost per m3 Ground water US$2.50 Surface water US$3.00 Desalinated water US$4.70

It is the policy of the government to keep the cost of water low and therefore the cost of production, particularly for desalinated water, is not reflected in the rates charged to the consumer. It was not indicated whether the cost varied among consumers so that commercial users paid a different rate compared to domestic users. Agriculture is not significant in Antigua, but water for agricultural purposes wherever possible came from


groundwater and rainwater cisterns. The Ministry of Planning estimates the difference between production and revenue costs to be US $8 million between 1997 and 2020. In light of this, the Antigua and Barbuda Government had considered investing in the exploration of increasing availability of surface and groundwater. Given the ever increasing demand, and the uncertainty of climate change and climate variability, however it is more likely that reliance on desalination will become even more significant. The APUA is the government statutory agency responsible for the administration and operations of the utilities in Antigua and Barbuda. It was established under the Public Utilities Act No. 10 of 1973. All policy and legislative developments is channeled through and falls under the jurisdiction of the Minister responsible for Public Utilities. The unique institutional arrangement of the APUA covers telecommunications, electricity and water. The role of the Water Division is to provide, protect and preserve Antigua’s water supplies. In an effort to fulfill its mandate the APUA invested in a desalination plant at Crabbs, which was commissioned in 1987 and at one time supplied over 70% of the water to the country (according to information posted on APUA’s website http://www.apua.ag/Apua/about_us.htm). In 1993, the APUA entered into an agreement with a private agency, Enerserve, operating a reverse osmosis desalination plant at Crabbs, to purchase from them approximately 0.5 mgd. In 2004, figures quoted by the APUA on their website suggested that the Antigua and Barbuda’s municipal water supply comprised by source:

Volumes of Water Produced Daily from Various Sources

The types of plants utilized in Antigua and Barbuda include a Multi-Stage Flash Distillation (MSFD) plant, now owned by Veolia Water, of France, as part of a dual, 18.2 MW electricity generation facility of APUA (which produces 2 mgd of water); and a number of reverse osmosis (RO) plants. The largest RO plant, located at the APUA facility at Crabbs, was designed, built, owned and operated by Enerserve, to be eventually sold over to the APUA.

The Government of Antigua and Barbuda is currently supplied by Enerserve through five reverse osmosis units, which provide water to the Water Division of APUA. Each RO unit has a capacity of approximately 200,000 imgd (750 000 l/d) each. These plants use seawater, which is returned to the sea after use. The possibility exists to utilize the discharge from the Enerserve plant as feed water for the MSFD plant of APUA, but this has not been pursued as yet. A feature of these units is that energy recovery has been incorporated into the design, thereby reducing operating costs.

Source Volume (gallons/day) Surface water (during non-drought conditions) 700,000 Reverse Osmosis Plant 2,000,000 Multi-Stage Flash Distillation 2,000,000 Groundwater (during non-drought conditions) 450,000

http://www.apua.ag/Apua/about_us.htm


Enerserve Reverse Osmosis Plant, Crabs��Antigua�

Water produced by Enerserve is pumped directly to storage on-site at Crabbs. This storage is provided by APUA but is currently insufficient for the production capacity at Crabbs. Additionally, leaks within the transmission and distribution network result in the loss of treated, desalinated water. The two MSFD units at Crabbs are part of a facility which generates electricity. The process is quite complex and utilizes low pressure and temperature steam from the exhaust of the steam turbine. This exhaust steam provides the thermal energy for evaporation of seawater. Seawater is the feed water utilized and is essentially distilled, with 38% of the feed water distilled (or desalinated). The brine (or reject water) from this process is returned to the sea. The desalinated water is treated further to increase calcium hardness, using limestone beds, and alkalinity, to reduce corrosion in the distribution system. The APUA has also installed a RO plant in the sister island of Barbuda. This plant was commissioned in March 2005 and has a capacity of 120 m3/day (27,000 igpd). Since its commissioning, the plant has had to be taken out of service for operational reasons related to voltage fluctuations, which resulted in the units starting and stopping frequently. It has been suggested that the complex computer controls used at this facility are difficult to repair and that no local capacity exists to maintain this system. Capacity building therefore remains a concern in both Antigua and Barbuda in relation to operating RO plants. As with several other utility companies, APUA prefers to engage in design-build-own-operate contracts with private companies, which involves a handing over of the facilities after a 15 to 20 year period. The cost of utilizing desalination for APUA is high owing to the costs of pipe and pump replacement, energy and chemicals (which averages to about US$400,000 annually). The cost of desalinated water alone (from the RO plants at Crabbs) is US$5.8/1000 gal. The cost of desalinated water from the MSFD Plant at Crabbs is US$7.36/1000 gal. These figures account for the cost at the source and do not include the costs associated with chemical, operations and maintenance, etc. High costs are also attributable to the cost of chemicals used to reduce corrosion, and also to the replacement costs for the corroded pipes and pumps. A number of privately operated RO plants exist in Antigua as well, including at St. James’ Club, Carlisle Bay Hotel, Rex Halcyon Resort and Jumby Bay resort. Bahamas: The islands making up the Bahamas stretch from 24º 15 N and 76º W. The total land area approximates 13,864 km2 with a population of about 324,800 (2005 est.). The Bahamas comprises 700 islands and cays, of which only 3 islands have significant water sources while some have no freshwater at all. Where groundwater is found in natural aquifers, there is concern that the threat of sea level rise can affect the water quality.


The options for water production therefore include high cost desalination options such as Multi–Stage Flash Vapor Compression Distillation and Reverse Osmosis; barging water to the islands in water tankers; distribution through underwater pipelines and reuse of treated wastewater (for small scale irrigation). Other alternatives include groundwater abstraction, (which is limited), and rainwater harvesting. The following diagram illustrates the typical profile of fresh, brackish, saline and hypersaline waters of the near and deep subsurface and in lakes and ponds that intercept the surface, in the Bahamas. It also indicates the vulnerability of the system, and the reason for concern over the impact of sea level rise on groundwater. The options that have been employed in the past, and which continue to some extent in some islands, include barging of water by tankers and some groundwater abstraction. However, economic development, particularly for tourism is dependent upon availability of potable water. Therefore, desalination, specifically RO utilizing seawater, is being embraced as the most viable option for the water demand of the Bahamas into the future, particularly given the scale of water production required. Other desalination feed water sources include brackish water from wells and a lake. Alternatives such as rainwater harvesting are not popular as an augmentation option because it is subject to seasonal variability, making supplies unreliable. Those options that are vulnerable to damage during extreme weather events are also generally unfavourable. Groundwater abstraction can be costly because of the required pretreatment, and also because it requires heavy capital outlay for land acquisition and maintenance. Land for this purpose also often has to compete with other economic development activities. The cost of desalinated water in the capital, New Providence is comparable with the cost of barging water in from a neighbouring island, and has the advantage of superior quality, reliability and sustainability. Thus, although it is recognized that water produced by RO is not cheap, owing to the pre-treatment and energy requirements of the process, and the fact that returns are poor with respect to serving small, scattered islands, RO continues to replace groundwater sources. Plans are underway to increase the number of RO plants across the Bahamas.

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Diagram of a Freshwater Lens in an Oceanic Island(Like The Bahamas)

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Although older forms of desalination technology exist, RO appears to be preferentially endorsed, and in the Bahamas, RO plants have been customized to use diesel fuel. The Bahamas is one of the countries in the region with the longest history of desalination. Distillation technologies for desalination have been employed as far back as 1958. After two plants were commissioned and subsequently failed, the following were established with greater success from 1961.

Historical Experiences with Various Desalination Technologies for the Municipal Potable Water Supply

Place Period Technology Feed water Output Cost (local

currency) Problems

Clifton Pier, New Providence

1961 - 1971 MSFD seawater, then borehole water

672,000 gpd (60% capacity; designed for 1.2 mgd)

$2.70/1,000 gals (excludes electricity and manpower costs)

Corrosion; cost

Bimini 1969 - 1974 VCD seawater Very variable: max 19,000 gpd but average 12,000 gpd

$14.50/1,000 gals

Sand blockages, scale, corrosion, mechanical failure

Blue Hills, New Providence

1972 - 1977 MSFD Borehole water

1.2 mgd (60% capacity; designed for 2 mgd)

$7-8/1,000 gals

Corrosion, scale, cost

New Providence

1977 - 1980 RO (Pilot project)

Lake Killarnery (6,000 – 13,000 ppm cl)

447,000 gpd (89% capacity; designed for 0.5 mgd)

$7.65/1,000 gals

Fed water quality; cost

The table above represents water provision by the national water utility, but several private entities have utilized desalination for their activities including private developments, hotels, marinas and at least one rum distillery, from the early 1970s. There is no specific legislation or regulation governing water production by desalination. The operations of the Water and Sewerage Corporation are regulated by the Water and Sewerage Act, while privately owned plants operate under franchise agreements (the Out Islands Act) in the Family Islands where water is re-sold. In the Family Islands, there is no other viable option for water production, so desalination is employed. There are no regulations governing groundwater and individuals may install facilities for their individual use. In other areas where ground water is available, it is utilized. Although there is no national policy regarding desalination, “the Water and Sewerage Corporation intends to maximize the use of desalinated water….” according to Acting Deputy General Manager, Mr. Glen F. Laville. The Water and Sewerage Corporation (WSC) has demonstrated a preference for private companies to build, own and operate RO plants because of the technical expertise and maintenance required for running these plants. This arrangement reduces the need for technical expertise, minimizing the cost and impact on the human resource capacity of the WSC. It is estimated that there are over 200 RO plants currently operational in the�


Bahamas. The following represents the output of water in some the islands from these�plants and the year in which each plant was commisioned:

Output of Some RO Desalination Plants within the Bahamas Location Start of Operations Volume output in

Gallons per Day Moores Island, Abaco 1996 20,000 (recently up to

30,000) Grand Cay, Abaco 1996 20,000 (max.) Waterfields, New Providence 1998 2,000,000 Black Point, Exuma 1998 15,000 Farmer cay, Exuma 1999 3,000 Bimini 2002 80,000 Inagua 2003 50,000 Exuma Emerald Bay Plant 2003 50,000 South Eleuthera 2004 75,000 Exuma george Town Plant 2004 180,000 Long Island 2004 60,000 Ragged Island 2005 2,000 San Salvador 2005 80,000 To date, there has been no negative public reaction to the quality of desalinated water. In fact, the Corporation has recorded an increase in consumption where desalinated water has replaced groundwater. The Water and Sewerage Corporation actively promotes desalinated water as high quality and better tasting than the water from the traditional sources. Given the long history of the country with desalination, and the plans to increase the use of RO for water production, there appears to be a comfortable level of social acceptance of this technology. Some of the challenges associated with the use of desalination are the vulnerability of the systems to natural disasters, disruptions to electricity, and the quality of feed water. Problems are also associated with corrosion and the high cost of replacement parts and laying pipes. Currently, there are 200 plants producing more than 1000 gal/day each; Club Med alone demands 70,000 gal/day while the local population requires 10,000 gal/day on the island of San Salvador. In some areas, the problem extends beyond the technology and is one of maintenance of the distribution network. In New Providence, for instance, unaccounted-for water is estimated to be as high as 50 percent. Projected expansion of desalination includes:

• A new RO plant in Blue Hills, New Providence with a capacity of 5mgd and increased capacity of the Waterfields Plant to 3 mgd – signed contract

• Installation and operation of a 3 mgd plant at Arawack Cay, New Providence and 400,000 = gpd plant in Central Eleuthera – negotiation in progress

• Proposed desalination plants for: south Eleuthera, Acklins, North and Central Long Island, Green turtle Cay, Great Harbour Cay, areas in Cat Island, Crooked Island and Long Cay – identified need

• Establishment of desalination plants for large, private developments for residents in Managua, Rum Cay and in other islands, pending approval of these developments – negotiation in progress


The way forward is seen as the termination of the system of barging water and the commissioning of new plants and total dependence on desalination. The following excerpt from the Nassau Guardian recently noted that “…..According to Deputy General Manager of the Water & Sewerage Corporation, Godfrey Sherman, the Corporation has plans to construct a new reverse osmosis plant, which is expected to take some six months to be completed. The new plant which will be able to convert five million gallons of salt water to fresh water daily, will not come on stream until 2006.

"Salt water would be removed from the ground in Nassau and converted into fresh water. A similar plant is located at Windsor Field and converts some two million gallons a day into fresh water. Right now, the Corporation is looking for a suitable location to build another plant, possibly at Blue Hills," Mr. Sherman announced on Monday. ”

Barbados: Located 13º 2 N and 58º 5 W, Barbados, lies outside the archipelago making up the Lesser Antilles. Barbados occupies approximately 431 km2 and has a resident population of about 272,700 (2004), making it one of the most densely populated countries in the world. The geology of the island which is dominated by a 300-foot limestone cap below the surface catchment areas allows for the percolation of rainwater into a natural aquifer according to the Government of Barbados State of the Environment (GODSE) Report 2000. Raw water is abstracted from this natural underground freshwater reservoir or from underground springs that drain into it. According to the GOBSE Report (2000) groundwater accounted for 79% of the total fresh water resources of Barbados and about 98% of water in the distribution system, prior to augmentation with desalinated water. Factors sparking concern over groundwater quality include:

• Salinity resulting from heavy abstraction to meet demand; • Leaching of agricultural chemicals such as nitrates, phosphates and pesticides; • Contamination by industrial liquid waste; • Contamination from domestic liquid waste due to the presence of fissures; • Indiscriminate disposal of soild waste in the Gully System which acts as

catchments for the recharge of the aquifers; • Landfill leachate reaching the water table.

In Barbados, of concern is the preferred method of solid waste disposal, which is sanitary landfilling. This significant source of potential contamination of groundwater can have implications for water quality, safety and public health. The solid waste disposal problems experienced are precipitated by demand, population pressures and space issues, which are typical of Small Island Developing States (SIDS) (GOBSE, 2000). Barbados has been ranked the fifteenth most water scarce country in the world. The decision to pursue water augmentation was made after an assessment of the water situation in Barbados during the period 1993-1994. It was found that an average of 160,000 m3/day of water went into the distribution system and that this was the minimum volume required to meet demand. Reduction in annual rainfall and downward fluctuations in rainfall over shorter periods resulted in the inability of the BWA to meet demand. A 1994/5 drought highlighted water supply shortfalls, supporting the exploration of water augmentation alternatives.


December to May is normally recognized as the dry months, compared with the rainy period from June to November. Comparison of rainfall data shows that from 1978 to 1998, the average rainfall has decreased from 1524mm (60 inches) to 1422 mm (56 inches), however, the population, their level of affluence and their water demand have increased. The demand for water covers not just the domestic requirements of this population, but also for the tourist industry, which accounts for a significant proportion of economic activity on the island. Agriculture, agro-processing and light manufacturing are also sectors with significant demand on the public water supply. The per capita demand for water has been approximated at 0.62m3/day. According to a 1978 “Barbados Water Resources Study” by Stanley and Associates Engineering Ltd. and Consulting Engineering Partnership Ltd., the average total rainfall available from groundwater, surface water, springs and run-off would be about 246, 000 m3/day (54.79 US mgd) and during a 1 in 15 year drought period about 155,000 m3/day (34.37 US mgd). By 1996, the average total demand for water was about 158,400 m3/day. The projected growth rate for the increase in demand was determined to be about 3% annually, which would mean an increasing deficit from 1997, leading to a deficit of 47,900 m3/day by 2005. There was concern that the water demand for purposes other than domestic usage, particularly for irrigation of golf courses, would exceed the projected allocation of 90,000 m3/day. The average rainfall estimated in the state of the Environment Study Report 2000 was estimated at 1,422.4 mm for that time period. Attempts to address the water problems in Barbados included protection of water catchment areas and zoning to control activities in sensitive areas. Other measures employed in the 1980s included reducing water pressure, temporary shut-off of water in various areas at various times, and a temporary increase in the tariff block. Between 1996 and 1998, the Water Resources Management and Water Loss Studies (WRMWLS) were commissioned to address the factors of: increased demand, increase in the use of potentially harmful agro-chemicals, and reducing rates of aquifer recharge rainwater due to run-off resulting from urban development. The major recommendations from this study focused on reducing consumer use of the resource and reducing water loss within the distribution system. In 1997, the Policy Framework for Water Resources Development and Management informed by the recommendations of the WRMWLS developed a comprehensive Water Resources Development and Management Plan with projections up to the year 2016 and beyond. This plan included strategies focused on demand and supply management, augmentation, institution capacity building, policy and legislation. Included in this plan was endorsement of desalination as a water augmentation option. In 1996 a feasibility study was commissioned prior to the establishment of the desalination plant in Spring Garden, by the Government of Barbados to address “….all aspects of water supply in Barbados, quantifying the need for additional water, considering alternatives for supplementing the natural groundwater..” The study indicated that source augmentation by the use of desalinated brackish water by reverse osmosis would be an appropriate alternative for Barbados. Some of the factors supporting that decision included:

• Supply and demand; • Hydrogeology; • Technology; • Financial and economic considerations; • Location and site selection;


Spring Garden Reverse Osmosis Plant Barbados

• Environmental impact considerations; • Management; • Operation and ownership; • Implementation.

Other water related issues factored into the implementation of the proposed system included the metering and unaccounted for water reduction programmes. Ionics Freshwater Ltd. (recently acquired by General Electric) has built, owns and operates one brackish water RO plant in Spring Garden (St. Michael). It owned another at Hope, St. Lucy, but this was closed in June 2004. The Spring Garden RO plant was commissioned in February 2000, and converts brackish water from 10 wells. By contractual agreement, Ionics/GE agrees to hand over ownership of the plant to the Barbados Water Authority (BWA) after twenty years, and, until then, agrees to sell its water exclusively to the BWA. Ionics/GE owns over 35 desalination plants in the Caribbean. Sandy Lane Hotel, in the parish of St. James, owns the seawater RO plant, built and operated by DesalCo, which is used primarily for maintenance of landscape and for irrigation of the existing world-class golf course.

The desalinated water from the Spring Garden plant is conducted into an underground reservoir from its storage tanks, where it mixes with chlorinated groundwater. The higher conductivity and nitrate levels of groundwater, when diluted with the desalinated water bring it to acceptable levels for these parameters, in accordance with WHO guidelines. The general public initially complained of unpleasant taste and slimy texture of the water, but after public education efforts, there now appears to be greater acceptance. While no changes were made to the quality of water, complaints declined to the point that

the public is now calling for increased desalination plants, according to the BWA. Currently, desalinated water accounts for about twenty percent of the stored water fed into the distribution network. The Spring Garden RO plant operates at 50% of its capacity, producing 6 imgd. Energy for the operations of the plant is derived from the national grid. The cost of the desalinated water is only slightly higher than the cost of treated groundwater. This is due, among other things, to the fact that the brackish water is of a relatively high quality (low salinity). Because of this relatively low salinity of the brackish feed water, the brine can be reintroduced via deep boreholes close to the coast, which does not cause salinity levels to increase beyond the normal range for the receiving body.��

The Barbados Water Authority boasts an island-wide distribution ne their own water but these are largely for agricultural and golf course irrigation, and be twork that provides access to 95% of all households. A small percentage of users supply verage manufacture. The Authority had to undertake an increase in water rates with the implementation of desalination along with other programmes addressing metering and unaccounted for water.


The Town and County Planning Department has to approve the plans and proposed operations of desalination plants, including conducting a full EIA and monitoring implementation. The department responsible for Development Protection in the Ministry of Environment is responsible for water quality issues and the Coastal Zone Management Unit (also in the Ministry of Environment) is responsible for monitoring the impact of discharges to the coastal ecosystem. As the Spring Garden desalination project was being developed, residents within a 1 km radius of the project were particularly addressed as stakeholders and informed of the project and the implications as part of the EIA process undertaken by the BWA. The disadvantages of utilizing RO desalination technology in Barbados include: 1. the cost and the fact that costs are tied to energy which is linked to rising oil prices; and 2. uncertainty of the long term viability of the source of feed water. With intense abstraction, if the levels of total dissolved solids rise sufficiently, the location of the plant could allow for sea water abstraction, but the cost of replacing the membranes and pumps would amount to construction of a new plant. Opportunities include the potential for developments in technology to result in a reduction in the cost. This could offset the cost of converting to sea water abstraction if that becomes necessary. Desalination as an augmentation approach is consistent with the policy of the BWA. It allows further access to unlimited and previously unusable brackish and seawater resources. British Virgin Islands The British Virgin Islands (BVI), located 18º 26' N, 64º 40' W in the Northern Caribbean, is about 60 miles east of Puerto Rico. This country is made up of 33 islands and cays in total, of which only about 16 are inhabited, but the 5 main islands are: Tortola, Virgin Gorda, Jost Van Dyke, Peter Island and Anegada. The total area is approximately 153 km2 and the total population is estimated at 22, 643 (July 2005 est.). The BVI comprise steep, hilly volcanic islands with the exception of Anegada ahich is a flat coralline island. The climate is described as tropical and is moderated by the Trade Winds. The rainy season is typically from May to November. Most of the economic activity surrounds the tourism industry, which accounts for about 45% of the national income and the registry of international companies. Some livestock rearing takes place and but arable farming is negligible because of poor soil quality. Forest and woodland accounts for only 7% of the vegetation cover. The average annual rainfall is about 1250 mm/year. Like the Bahamas, the BVI has limited freshwater resources. Most of their water comes from a few seasonal streams and springs, wells on Tortola and rainwater harvesting. In order to address the developmental needs of the country, particularly on the drier islands, water augmentation was a major issue. As in other islands where this is a traditional problem and not an emergent one, there have been several methodologies employed to adapt to this situation. Rainwater harvesting has been employed, but this would not be feasible for large scale application like the tourism industry. The Water and Sewerage Department, is part of the Ministry of Communications and Works, which provides 95% of the population with access to water. 90% of water consumption is from domestic users. The estimated water out put is approximately 2 imgd. Currently, there are 8 desalination plants in operation in the BVI. 7 of these plants are RO plants and are owned by private companies, while the sole multi-stage flash distillation


system is owned by the local Electricity Corporation, which is a statutory body. Companies typically enter into an agreement with the government whereby they agree to supply desalinated water for a period of between 7 and 15 years, with options for renewal, termination, or purchase of the plant in some instances. All the desalination plants are established under build-own-operate agreements. The government in most cases, will allocate state-owned land for the siting of the desalination plant. Since desalination is viewed by the government as their sole means of satisfying local demand, its policy is to support all efforts towards that end. The Water and Sewerage Department indicated that the reject water from the various desalination plants is disposed of in the open sea, with no negative impacts to the environment. It is therefore assumed that some form of assessment was carried out to make that determination, although a specific reference to such an assessment was not made. Desalinated water is purchased by the government at an average cost of US $18.60/1000 g (imperial) but the actual cost can range between US $9.00 – US $20.00 per 1000 g. Water is then sold at different rates depending on the customer.

Cost Structure for the Sale of Water to Broad Categories of Users in the BVI

Domestic Rates per gallon 1st 1,000 gallons US $0.012 2nd 1,000 gallons US $0.015 3rd 1,000 gallons US $0.015 Over 1,000 gallons US $0.018

Commercial Rates per gallon 1st 150,000 gallons US $0.025 2nd 150,000 gallons US $0.020 Over 150,000 gallons US $0.015

Government Standard Rate per gallon Unspecified volume US $0.018

An indication of the social acceptability of desalinated water is measured by the Department as the number of connections to the system. For a population of just over 20,000 people, there are 8,000 registered connections. Further, in the BVI, household often maintain 2 connections: one to the mains and another to a household cistern. The Water Department has indicated that feedback from several households suggest desalinated water is the preferred source. Plant operators and all but one manager is local. Given the heavy dependence and long history with desalination in the BVI, it is not surprising that they would build local expertise for the operation and maintenance of the plants. Trinidad and Tobago The twin island Republic of Trinidad and Tobago, the most southerly of the Caribbean Islands, lies between the Caribbean Sea and the North Atlantic Ocean, northeast of Venezuela and has a total area of approximately 5,128 sq km, and an estimated population of 1,088,644 (July 2005 est.). Its geographic coordinates are 11 00 N, 61 00 W


and it enjoys a tropical climate, with a rainy season from June to December, annually. Its terrain is dominated by plains with some hills and low mountains. The economy of Trinidad and Tobago is largely fueled by its natural deposits of petroleum and natural gas and much of the industrial activity surrounds these resources. Agriculture also plays an important role, and tourism is expanding, although it is more significant in Tobago. The industrial activity has implications for the water resources both in terms of demand and pollution. The Water and Sewerage Authority (WASA) is a government owned and operated statutory authority, established under the Water and Sewerage ACT of 1965. Under this Act and subsequent amendments, it is exclusively responsible for the provision of water and wastewater services to Trinidad and Tobago. Currently, most of the potable water distributed by the WASA comes from surface and groundwater water sources (65% and 25% respectively) and desalination (10%) and WASA claims 92% coverage of Trinidad and Tobago. The authority estimates that 45% of the water entering the distribution system, but not generating revenue is unaccounted for due to technical faults such as leakage, while 6% is as a result of illegal access of the resource by persons. Other problems identified by the Authority are what they refer to as an unrealistically low tariff structure and a poor collection policy. There was an annual increase in water production from 1997 to 2002 (276.8 to 346.7 million gallons), but despite this, there was still a net deficit with respect to demand during this period.�� WASA’s assets that relate directly to drinking water are: 23 surface water treatment facilities; 53 groundwater treatment facilities; 48 rural intakes and spring sources; 120 pumping stations (booster stations); approximately 6,000 kilometers of water mains (pipeline) ranging from 20 mm to 1,350 mm in diameter; 4 raw water impounding reservoirs: total storage of 68 million megaliters (15 billion gallons); and 436 wells. Daily water production is of the order of 210 mgd. This represents a 217% increase over 1965 volumes. In Tobago, an increase in potable water availability is projected, particularly in response to increased needs for the Tourism sector. There has been an increase in water production in Tobago from 27.3 megalitres (6 million gallons) to 40.9 megalitres (9 million gallons), over the last 5 years, and an increase to 12 54.5 megalitres (12 million gallons) was projected for this year. The Government of Trinidad and Tobago, in its efforts to ensure a reliable water supply to the Point Lisas Industrial Estate on the west coast of Trinidad and which houses the heavy petrochemical plants, commissioned the construction of a desalination plant in the late 1990s. Prior to the establishment of the desalination plant, however, a study was conducted to evaluate the other options for water augmentation for the Point Lisas Industrial Estate. 14 other sources were assessed and it was determined that desalination was the best option. This study was undertaken by WASA in 1997. The recommendation of this study led to the decision by the Government of Trinidad and Tobago, to establish a desalination plant at Point Lisas. The plant at Point Lisas is privately owned by the Desalination Company of Trinidad and Tobago (Desalcott), which is a joint venture between Ionics Inc. of Massachusettes, USA (40% share) and Hafeez Karamath Engineering Ltd. of Trinidad and Tobago (60% share). Desalcott is the largest desalination plant in the Caribbean at present. It cost an estimated US $150,000,000 and employs about 80 persons full time. The plant occupies 7.5 hectares of land. Part of the establishment of the desalination plant included the construction of a new transmission line to WASA’s distribution network. When the application was made to the Town and Country Planning Division for the proposed desalination plant utilizing Reverse Osmosis technology to convert seawater


Aerial View of Desalcott Reverse Osmosis Plant, Point Lisas Industrial Estate, Trinidad

from the Gulf of Paria to the West of the Trinidad, it was stipulated that an Environmental Impact Assessment (EIA) was a requirement because of the magnitude of the project. A private engineering consulting firm was selected to undertake an extensive EIA that considered impacts during both the construction and operational phases and looked at issues including wastewater, solids, shipping, siltation, the economy, services and utilities, social impacts, public safety, fishing, coastline development, air quality, noise, and geotechnical factors.

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This EIA was perhaps the most extensive EIA ever done for a desalination project in the Caribbean. (In the most of the other countries from which information was sought, there was no indication that an EIA was required or conducted.) According to the EIA, Desalcott satisfied all the parameters stipulated to ensure safety to the public and the environment. The product water was found to contain less than 85 mg/l contained of totally suspended solids, which is considerably less than the WHO guidelines figure of 500 mg/l; and 55 mg/l of chlorides. The temperature of the water is also less than 35ºC, although it is slightly higher than ambient water temperature. The reject water is returned to the Yara Trinidad Limited (formally Hydro Agri) outfall channel via an outfall pipeline. Yara is a private international and multinational company, involved in the manufacture and distribution of nitrogenous fertilizers. The reject water from the desalination plant is thermally elevated as is the waste from Yara Trinidad Ltd. The EIA indicated that the additional output from Desalcott would not have a negative impact on the coastal or marine environment, particularly as it related to the nearby mangrove as long as the combined effluent concentrations of a variety of contaminants did not exceed 40 ppt. Solids derived from silt emanating from the filtration process are treated and transported to a local landfill. Desalcott has indicated its intention to apply for this material to be classified as a by-product, which can then be reused. The plant emits no noxious discharges.


THE USE OF DESALINATION PLANTS IN THE CARIBBEAN - 2006

The schematic diagram below outlines the reverse osmosis desalination process as it operates at Point Lisas and provides details of the pretreatment which removes much of the particulate matter or sediments from the feed water. Desalcott is contractually bound to sell water to the Water and Sewerage Authority (WASA) for 20 years, commencing from the establishment of the plant in August 1999, until it is sold over to WASA. As with most other Caribbean countries, WASA entered into a build-own-operate arrangement with Desalcott. At the time that the desalination plant was conceptualized, it was the intention that it serve as a dedicated water source for the Point Lisas Industrial Estate, although its water could be made available to other WASA’s other customers. According to WASA’s 2005 Prospectus, 109,090m3 of water is purchased daily. This RO plant supplies high quality water, which is more expensive than the domestic water produced by WASA from surface and groundwater sources. �

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According to the Trinidad Guardian, June 24, 2004, there has been an ongoing dispute between Desalcott and WASA leading to arbitration, over the price paid to Desalcott by WASA for water. This stemmed from the claim by Desalcott that the company was entitled to a 10% increase in the cost of water during the first year of the contract. The initial price paid for water from Desalcott was US 0. 71/m3 and the increase would see a change in cost to US 0. 78/m3. 70% of the water from Desalcott is resold to the petrochemical plants at Point Lisas at US $1.17/m3. The current cost is reported by Desalcott asbeing one of the lowest in the world for desalinated water. In 2002, 13% of the WASA’s expenditure was from the purchase of water from Desalcott. The tariff structure recognizes 2 major categories: domestic and non-domestic users. These groups are further subdivided by activity or the type of premises. It is not based on the cost of producing or supplying water to the particular class of customer, except where desalinated water is purchased from Desalcott and resold to Point Lisas Industries. The tariff structure was implemented in 1993 and varied depending on variables such as whether the users were metered or un-metered, domestic (TT $1.75m3), agricultural, commercial, industrial, charitable organisations, etc.

Schematic Representation of RO Process at Desalcott Plant, Point Lisas, Trinidad


According to the Regulated Industries Commission’s Review of the Status of the Water and Sewerage Authority, about half of the 22 mgd generated by Desalcott is made available to the Point Lisas Industrial Estate. By Desalcott’s estimation, Point Lisas industries consume on average, 70,000 m3 per day. The Ministry of Public Utilities and the Environment is responsible for policy formulation and the granting and revocation o licenses to water providers. WASA has to seek approval from the Ministry of Finance for any large capital projects as the Government will either allocate such funding from the national budget, guarantee loans from the commercial sector, or, in conjunction with the Ministry of Planning and Development, will seek funding from international agencies. The Ministry of Health is responsible for monitoring and enforcing the WHO guidelines for drinking water safety, in the absence of national standards. The Environmental Protection Authority (EMA) is a statutory body, established by the EMA Act of 1995 to address environmental protection and conservation including the monitoring the effluent levels and from trade activities including effluent from the desalination plant. WASA continues to explore and increase its production of potable water. They have projected to replace the pipeline network as part of its commitment to improving the service provided to customers, and meeting the Government’s 2020 Vision Objectives. � St. Lucia St. Lucia is approximately 616 km2 and is one of the Windward Islands making up the East Caribbean Archipelago. Its coordinates are 14 N, 60 W; and it lies between the islands of Martinique to the north and St. Vincent to the south; and approximately 100 miles northwest of Barbados. The island is volcanic in nature and is dominated by a mountainous interior with several coastal and river valleys. The country enjoys a tropical maritime climate with a wet season from June to December and a dry season from January to May annually. Rainfall varies widely across the island, so that annual rainfall for the extreme northern and southern ends of the island approximate 1,200 mm while the more mountainous central region sees about 3,500 mm annually. Most of the rainfall is drained to the sea via surface channels, as there are no natural lakes or ponds for water collection. Most of the economic activity in St. Lucia surrounds the tourism sector, agriculture, some manufacturing and offshore banking. The population is particularly dense in the north of the island in the districts of Castries and Gros Islet. The rate of growth of the tourism sector places demands on the water resources of the island. Many of the larger hotels and resorts are located in the north of the island as well. The supply of potable water is the responsibility of the Water and Sewerage Corporation (WASCO), which is a statutory board responsible for provision of water to the public and for securing within the parameters of the legislation under which it was established, to secure the resource for projected demand. The Water and Sewage Act of 1999 is the legislation governing WASCO’s operations. Under this Act, a National Water and Sewerage Commission was appointed by the government. The function of this commission is to oversee the provision of licences for water abstraction, make recommendations to the responsible Minister for water resources preservation, regulation (with respect to quality, standards and economics), handle public complaints, affix tariffs to water and sewage services and maintain information related to water resources in St. Lucia. 2001 census data and WASCO reports suggest that 90% of the population has access to water from the Company (including illegal connections). About 36,000 households are legally connected to the distribution system.


WASCO is allowed to undertake its functions for 25 years commencing from the commencement of the Act, and is also expected to carry out government policy in relation to water supply and sewerage and provide the public with dependable sewerage services, and to provide the public with a safe, adequate and reliable supply of water. WASCO also has responsibility for conserving, redistributing and augmenting water resources in St. Lucia, in conjunction with the Water and Sewerage Commission. The Water Resources Management Project was developed to facilitate water resource assessment, watershed management, rationalisation of existing institutional frameworks and public awareness and sensitization. In order to secure the quantity and quality of water, WASCO can declare certain areas forest reserves or protected forests in accordance with the Forest Soil and Water Conservation Ordinance, Cap 25; or controlled areas under section 36. WASCO may also request that action be taken by the Ministry of Health, through the Minister, under the Public Health Act of 1975, or related legislation, to prevent and regulate threats to any gathering ground. To improve water management, the government also established policies for the development of National Coastal Zone Management, National Water and National Land Use Policies. WASCO does not at this time utilize desalination was a water augmentation option, and currently, there is also no official government policy regarding desalination. However, the Government did consider the establishment of a desalination plant in the north of the island to address the inability of WASCO to meet demand in this area, as part of a comprehensive strategy to strengthen the water sector. The Gros Islet district in the extreme north of the island is home to a number of major hotels and resorts, and also to some of the more affluent sectors of the population. There is also tremendous potential for further physical development, but water constraints have limited construction activity. Water feeding the north comes from the Roseau Dam which has a capacity of 750 million gallons, while the output of the Theobalds Water Treatment Plant which it feeds is approximately 6.0 imgd. This supplies about 80% of the 86,000 residents in the north of the island. In 2005 an environmental assessment was undertaken by the World Bank in order to determine which of two options presented would be most appropriate to improve water availability in the north. One option proposed increasing the capacity of the existing distribution; while the other spoke of implementing a mobile desalination plant at Pigeon Point in Gros Islet. Ultimately, the capacity upgrade alternative was selected because it was determined that this would address the water needs of not just the problematic area but would serve a wider area beyond for the next 10 – 15 years, with fewer potential environmental impacts. It would also do this at lower cost. The desalination plant would have produced 20,000m3/day and incurred a cost that would then be passed on to all consumers, so that poorer sectors of the population would essentially be subsidizing water for the more wealthy sectors. The energy demand of the desalination plant was another concern. It was also predicted that water dedicated from the desalination plant to serve a specific area, which also has a high growth potential would fuel construction activity thereby driving up water demand beyond the anticipated figures. The proposed site for the desalination plant was in an area that has archeological and historical significance. It is also a particularly picturesque location and thus important for the tourism industry. There were also concerns that the sensitive environment would be irrevocably impacted upon. The site would have occupied 2,200 ft2 and would require


electrical and back-up generator support as well as a connection to the WASCO distribution mains. Desalination plants are used by at least 2 resorts in St. Lucia with approval for another currently pending. The type used in both cases is reverse osmosis. The newest Sandals resort, Sandals Grande St. Lucian Beach Resort and Spa on the Pigeon Island Causeway uses desalination sporadically to make up for shortfall in supply by WASCO. Ti Kaye Village Resort, a smaller property on the west coast of the island where WASCO’s distribution network does not extend, uses brackish water as the feed water. In the case of Sandals, their desalinated water is mixed with water supplied by WASCO in storage. The plant used by Ti Kaye, which is touted as being the first on the island, utilizes energy of about 162 kwh/day and produces 6,000 imperial gallons/day. The resort owns and operates its plant, which was commissioned in 2001. Although staff received no specific training save what was provided by the manufacturer upon installation, they are confident that they have the experience and expertise to operate and maintain it. The ratio of brine to product water is 50:50 using membranes at 6000 psi. They do not treat with chlorine, but they do use an anti-scalant and treat periodically with acid and alkaline solutions. The main issue observed with this operation, is the discharge into a shallow ravine, in close proximity to a mangrove. It was revealed by the resort management that neither the Ministry of Planning nor any other local agency was involved in the planning, approval, review or implementation of this desalination plant. St. Lucia has recently adopted a Water Sector Policy and re-established a Water & Sewerage Commission, to regulate water supply and improve water resources management. Efforts to improve water supply include encouraging additional investment in the sector and licensing of additional operators. It is expected that new service providers will come on-stream in the future and it remains to be seen what options will be explored. WASCO however is exploring the option of increased groundwater exploration and it is felt that this provides great potential, once tapped. There therefore seems to be limited potential for desalination making a serious dent in the traditional water supply market in the near future, bearing in mind the relatively higher cost of desalination over groundwater abstraction. However, it has been observed that proposals for the establishment of new plants have to be evaluated by the Ministry of Planning and the other regulatory agencies and CEHI, prior to construction. Grenada The Tri-Island State of Grenada, Carriacou and Petite Martinique is located 11° 58′ north latitude and 61° 20′ west longitude and has an area of about 345 km2 with a population of approximately 104,814 (2003). Grenada displays the typical volcanic topography with the characteristic mountain ranges. Carriacou also has a few significant elevations. Petit Martinique, however, is of lower topography. Whereas Grenada has significant surface and spring water sources, the islands of Carriacou and Petit Martinique do not have such resources and rely heavily on rainwater harvesting and to a much lesser extent, on groundwater. �

The National Water and Sewerage Authority (NAWASA) of Grenada has the mandate for the supply of potable water and currently manages 3 reverse osmosis desalination plants costing a total of EC $12 million: one in Grenada, one in Carriacou and one in Petit Martinique. These plants are roughly 5 years old with the one with the smallest capacity (30,000 gpd) located in Petite Martinique. Carriacou has an output capacity of 100,000 US gpd; and the plant in Woburn, Grenada was designed for an output of 400,000 US gpd.


RO Plant in Petit Martinique

RO Plant in Carriacou�

On the mainland Grenada, as in St. Lucia, the plant was erected to augment the existing available surface freshwater sources which is abstracted to meet the public demand. In Carriacou and Petite Martinique the main source of freshwater is rainwater and the desalination plants were built with the aim of providing a reliable and secure source of freshwater especially during the dry season. All of the plants were originally purchased by the Government of Grenada from American Engineering Services (AES) and turned over to NAWASA. �

During the site visits to these plants between November 16 and 18, 2005, none of the plants were operational. In Grenada, the plant located at Woburn, in the south of the island, had not yet been commissioned. There have been several setbacks related initially to the location of this plant. In Carriacou and Petit Martinique, the plants have been commissioned, but appear to be plagued with a number of operational and maintenance problems. Interviews with NAWASA revealed that there is no service contract with the manufacturer, and as a result, any technical assistance required is at full cost to NAWASA.

Currently, desalination may appear to be good water augmentation option for the water scarce islands of Petit Martinique and Carriacou, but in practice, there have been several problems. These islands have no surface water however; some groundwater is abstracted through boreholes and made available to about 10 % of the residents in Carriacou. The boreholes often contain brackish water and their locations are largely inconvenient since there is no distribution network, save for a small area in Hillsborough, the main town in Carriacou.

Water for most purposes is derived from rainwater harvesting, which is extensively practiced on the two small islands. There are communal rainwater harvesting systems, but most are in a state of disrepair. Most persons and businesses, agencies etc. have individual rainwater harvesting systems and cisterns. The level of technology employed depends on the economic status of the residents and range from rooftop catchments with concrete or metal cisterns constructed within buildings and underground, to plastic water storage tanks located outdoor, to metal or plastic 55 gallons drums. The existence of individual household rainwater harvesting systems and the associated level of convenience, competes with the fact that the desalinated water has to be trucked to the user at his own cost. In the islands of Carriacou and Petite Martinique there is also a


Severe Corrosion of Metal Surfaces at the Petit Martinique RO Plant

history and culture of sourcing “free water” so payment for desalinated water is a deterring element to the consumers and therefore it has to be heavily subsidized. Desalinated water is currently offered at EC $0.02/gallon when the actual cost of production is closer to EC $18-20/1000 gallons. This figure is derived from the energy costs of about EC $8.00/1,000 imperial gallons; and from the cost of maintenance, consumables and replacement parts (including costly chemicals and membranes, filters etc.) and operations costs, all of which total about US $50,000 per month (not including shipping). This estimate is based on a similar plant in operation in Cyprus. For the Carriacou plant, which has a storage capacity of only 10,000 gallons, and an output capacity of 100,000 gpd, the annual expenditure as it relates to maintenance would be about EC $269,469.53.00 (excluding operations and shipping costs).There was no service contract with the manufacturer, so as a result, NAWASA is forced to use its resources for all operations and maintenance costs, making the cost of desalinated water highly subsidized. The acceptance of desalinated water as a potable source is major hurdle facing NAWASA in Carriacou and Petite Martinique. There exists the public perception that rainwater is safer and healthier than desalinated water and when available the desalinated water is mainly used in the construction sector. A random survey carried out within several communities revealed that, even under drought conditions, persons were reluctant to consume desalinated water. Whereas, most had never tasted the water, they complained that they did not like the taste of NAWASA’s water from the mains in Grenada due to the chlorine treatment. Some complained that they had never been advised that desalinated water was safe for consumption. Additionally, the capacities of the storage tanks for the desalinated water in Petit Martinique and Carriacou are insufficient, making production of potable water a function of the immediate demand. Because the demand and storage capacity is relatively low, the plants are often unused for long periods at a time, and that has proven to impact negatively on their efficient functioning, leading to frequent need for servicing. The alternative is to produce water that is then discarded, in order to keep the equipment running. Either way, there is a significant cost incurred by NAWASA.

In addition to the problems already identified, the plants all utilize seawater as their feed water and are thus positioned on the coast. One of the problems identified by NAWASA is that damage to the suction pipes resulting from severe weather conditions. Location of the plants has also been the subject of much debate because of the noise associated with the operations however, the potential impacts of brine disposal was less

debated.


The quality of feed water was also cited as a problem in Petit Martinique in particular where the plant was located in an area that saw the accumulation of tidal debris from land-based and marine sources. This plant also showed evidence of severe corrosion on the outside metal structures. There was no impact assessment carried out prior to the siting of the plants. There is no official policy, legislation or regulations specifically addressing desalinated water, however, under the National Water and Sewerage Authority Act (1990), NAWASA is given authority over all surface water and groundwater in Grenada.

According to this Act, the Authority shall have full power over all waters whether surface or underground in the State of Grenada, and shall collate and publish information from which assessment can be made of the actual and prospective water resources in the State. Additionally, the Authority shall, unless unavoidable, be responsible for the provision of a satisfactory supply of potable water for domestic purposes and an otherwise satisfactory supply of water for agricultural, industrial commercial purposes and for such other purposes as may be prescribed by the Minister.

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Essentially, the Act covers all areas such as the institutional arrangement of the Authority and the administration of the powers vested in this body, the powers of entry and acquisition for water and sewerage works, financial provisions, rates and charges, acquisition of property and wells and boreholes. Catchment areas are given emphasis and measures for the protection and conservation are outlined along with the collaborative arrangement with the Ministry of Agriculture Forestry Division for the management of these areas. The fact that the Government invested in the reverse osmosis plants seems to suggest that there is a definite tendency by the political directorate to opt for desalination as a means of source augmentation and rely less on traditional surface, ground and rainwater sources. A few hotels and resorts e.g. in Culligen have small desalination plants which they have erected to augment their water supply. It is assumed that this is more feasible than for the municipal supply because the actual costs can more easily be passed on to the consumer. Mexico: The country has been divided into 653 hydro geological units or aquifers, 102 of which are overexploited. Moreover, there are 17 aquifers with salt-water intrusion problems, located in Baja California, Baja California Sur, Colima, Sonora, and Veracruz. During the study it was detected that before thinking of acquiring a desalting unit in Mexico, it is necessary to consider the following aspects: seriousness of the company, which offers the service and technical support, technical competence, previous experience, continuous operators training schemes, system complexity, and the consideration of a pre-treatment unit as a fundamental part of system operation. In the next years it is predicted that Mexico will have a low water supply availability (between 1000 to 5000 annual cubic meters per person, equivalent to 3 to 15 m3 per day)[1] With this scenario, the Mexican government has taken actions to solve the problem. In 2004, the government gave the first concession for the municipal largest


desalting plant in Mexico, 200L/s for Los Cabos in Baja California. The cost of this plant is 25,000,000 EUROS, this plant is going to operate on September of 2006. To December 2003, 203 desalting plants have been reported in Mexico. However, part of them are being operated by municipalities and do not work appropriately, due to the lack of qualified personnel, poor service from the suppliers, administrative problems and high operating and maintenance costs. Just to mention a single case, in the State of Quintana Roo (south of Mexico) there exist some plants of reverse osmosis located in Xcalk near Chetumal, or Contoy Island, which are practically abandoned. The following table shows the results of the survey in order to know the number of desalting plants in the country to December 2003.��

National Inventory of desalting plants in Mexico include installed capacity, whether

the plant is in operation or not and the operation capacity��

State Desalting plants

% National Operate Installed capacity

Operation capacity

Yes No m3/d m3/d

Baja California 10 4.95% 7 3 9,540 8,040

BCS 38 18.81% 32 6 8,979 3,346

Campeche 3 0.99% 1 2 3,120 750

Coahuila 7 3.47% 2 5 78 31

Durango 24 11.88% 9 15 650 374

Guerrero 4 1.98% 2 2 2,000 900

Nuevo León 2 0.99% 2 0 325 325

Oaxaca 1 0.50% 1 0 13,478 13,478

Q. Roo 107 52.97% 88 19 38,995 23,266

SLP 1 0.50% 1 0 60 5

Sonora 5 2.48% 4 1 471 80

Tamaulipas 1 0.50% 1 0 1,728 363

Total Country 203 100% 150 53 79,424 52,340

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According to the data, desalting capacity in Mexico is around 79,424 m3/d (919 l/s). Sixty four percent of the desalting plants belong to private owners, mainly of the tourism industry. States that present an important growth in these units are Quintana Roo (Cancun and the Riviera Maya) and Baja California Sur (Los Cabos), mainly due to new


projected tourist developments. The technical and economic study of the processes demonstrated that the reverse osmosis is an economic option for desalting seawater and brackish water in Mexico, because the new techniques for the energy saving are available and the membranes have improved. Production costs have been obtained up to 0.39 USD/m3. Twenty six percent of the desalination plants do not operated. �

The following table shows the desalting plants per process and State where the plants are located.

Desalting plants per process and State of location

State Delsalting

plants Process

RO VC MSF Solar Solar

experimental [2]

Baja California 10 3 4 1 2 0

BCS 38 32 3 0 2 1

Campeche 2 2 0 0 0 0

Coahuila 7 7 0 0 0 0

Durango 24 24 0 0 0 0

Guerrero 4 4 0 0 0 0

Nuevo León 2 2 0 0 0 0

Oaxaca 1 1 0 0 0 0

Q. Roo 107 106 1 0 0 0

San Luis Potosí 1 1 0 0 0 0

Sonora 5 4 0 0 1 0

Tamaulipas 1 1 0 0 0 0

Total National 202 187 8 1 5 1

RO: Reverse osmosis, VC: Vapor compression, MSF: Multistage Flash Destilation The most popular system for water desalination in Mexico is reverse osmosis, with 52% of the plant. 60% of the desalting plants (121) are for hotel uses, with 38,878 m3/d (450 l/s), 30% for municipal uses (61) (213 l/s) and 10% for industrial uses with a installed capacity of 256 l/s).


Conclusions Why desalination? Desalination appears to have been chosen as an augmentation source, where the public utility is either unable to or unwilling to provide water in sufficient quantity to the client. In some cases, the public utility simply does not have the capacity to provide in sufficient volume for the needs of some larger customers (e.g. industry in Trinidad or hotels elsewhere in the region). In other cases, the islands are so remote from a central supplier that it has proven more cost effective to set up small units for these communities (e.g. Bahamas family islands; Barbuda). In these situations, the lack of adequate rainfall or sufficient alternative water sources requires that brackish or seawater be utilized. Types Two main categories of desalination technologies exist: thermal and membrane technologies. Thermal technologies rely on heat as the name suggests, and essentially require increasing the heat and reducing the pressure of the feed water to cause vaporization, then cooling to cause condensation of the vapour to produce fresh water. The main types that are offered commercially are: Multi-stage Flash Distillation; Multi-effect Distillation and Vapour Compression Distillation. Reverse Osmosis is just one type of membrane technology. Other types, which are not common in the Caribbean include: Electrodialysis and Electrodialysis Reversal. Desalination plants are mostly of the RO type in the region. One company alone has supplied over 35 of these plants to various clients. These plants have been installed for small communities and for large industrial parks. In fact the largest desalination plant in the Caribbean is a reverse osmosis plant. Their modular construction allows them to be sized for various uses and production rates. The distillation-type desalination plant has also been utilized to a limited extent. In Antigua, a Multi-Stage Flash Distillation plant, consisting of two desalination units has been in operation since the 1980s. This plant is part of a co-generating facility, which uses excess steam from an electricity generating plant to produce desalinated water. In the absence of the co-generation, it is unlikely that this type of facility would be competitive in price with modern RO plants. A similar system exists in the Bahamas, owned and operated by the Water and Sewerage Corporation. Challenges The major challenge in relation to desalination has been the significantly higher cost of producing potable water, compared to traditional sources. Additionally, the technology has not been well understood until perhaps more recently, and therefore the operation of such facilities has been left to those considered highly skilled. Even when the Build-Own-Operate-Transfer (BOOT) approach is taken, it has not always been exercised due to high maintenance costs and inadequate training within the public utilities. Operational difficulties have been reported such as voltage fluctuation, which has resulted in production capacity being reduced at times. Another operational problem related to sand passing through a filter and destroying the membrane in some units. Water pressure fluctuations have also resulted in filter damage, requiring new filters, of a different design, to replace those damaged.


Most desalination plants in the Caribbean are located close to the sea. As such, general corrosion problems have been observed with metal parts and equipment, requiring more regular maintenance. In Grenada, destruction of the suction pipes during bad weather have also been a problem. Opportunities Desalination plants, particularly RO plants, are becoming increasingly easier to operate. Additionally, the cost of the technology seems to be going down, which is making desalination more affordable. The increasing cost of energy however remains an on-going challenge and may be canceling out any gains made with respect to capital cost of RO plants. One particular water utility has been considering the use of desalination in order to offer expanded commercial services to hotels, in particular. Based on the difference between commercial rates and domestic rates, it seems to be a business opportunity worth pursuing. Legal and regulatory overlay Across the region, there is an emerging trend towards privatization of water supply and increasing the competition within that sector. Desalination fits nicely within that particular framework, where governments seem more willing to license private operators and even engage in exclusive contracts with these operators, to supplement water produced by public utilities. In most cases, operators of desalination plants must meet certain regulatory requirements. However these requirements are generally related to the public interest, such as protection of public health and the environment, and have not acted as deterrents to the growth of desalination. Socio-Economic & environmental setting Desalination has been an attractive option in the countries of the region with higher per capita income, or at locations considered to be of high revenue-generating potential. This is related to the higher cost of desalination compared to traditional water supply sources. Typically desalination has been used in countries which have large tourism infrastructure or where heavy industry, requiring large amounts of process water, is present. In the current economic environment in the Caribbean, it is likely that desalination will remain a last resort, when compared to alternative sources such as surface water, groundwater and rain water. The environmental impacts of desalination have been studied and have been generally found to be minimal. The Caribbean has a long history of using desalination now and is better able to assess the potential negative impacts. Public acceptance appears to be high for this technology. Where this has not been the case, the problem stems from the lack of public education. Of note is the potential for contamination of raw water used for desalination in co-generating facilities (e.g. from oil). Future potential The tourism industry, in particular, appears to present the greatest opportunity for utilization of desalination. Visitors to the region usually expect to be able to enjoy their vacation without having to ration water. As such, investors in the tourism industry seem


willing to consider desalination as an alternative source of supply when the public supply cannot be guaranteed or is unreliable. As the water sector deregulates itself, more opportunities for private sector operators will emerge. This should ultimately benefit the consumer, as these private sector operators will need to provide a competitive product. This may lead to improved technology for desalination, in order to reduce the cost of production. Given the fact that RO plants use comparatively less energy, it appears as the patterns already indicate, that this will be the best option for exploitation where desalination is undertaken or expanded. Improvements to the membranes to improve durability and reduce the cost, would have the effect of not just retaining its popularity as the technology of choice, but would quite likely increase the use of this technology in the region.


Recommendations� This study has revealed a few gaps and weaknesses that should be addressed as the countries go forward with desalination as a water augmentation option. At the policy level, the national government is strongly encouraged to develop a policy position where desalination is concerned so as to manage this water augmentation option in the scheme of other policies and plans already in place for this resource at the national level. There should be clear policies and procedures for the application process, and evaluation and review of the application taking into account environmental and social factors, once it has been determined to be economically feasible. Also important is monitoring of the plant to ensure compliance with public health and safety standards and guidelines, and environmental protection laws and regulations. These procedures will be useful particularly where the national water utility does not manage or is not involved in desalination and private entities undertake to pursue this option. It is important that the interests of all the relevant stakeholders are represented and that ultimately, decisions made that fall within the national policy and recognize sustainability issues. All attempts should be made to share information and lessons learned, particularly for knowledge transfer from countries with a longer history, more experience and more expertise to their less familiar counterparts. Where technological adaptations have yielded advantages or increased efficiencies, there should be a medium for sharing this information. Apart form professional associations that provide some of this type of sharing, such as the Caribbean Water and Wastewater Association (CWWA), this medium should go further e.g. facilitate the development of model legislation. The Caribbean Basin Water Management Programme (CBWMP) may be such an instrument. The situation in the Grenadine Islands of Petit Martinique and Carriacou has demonstrated the need to educate the public and the success of this approach in Barbados supports this point. This is necessary for countries where desalinated water in being introduced to a population that has traditionally relied on other sources, and where myths or lack of knowledge of desalination may have produced negative perceptions. Public information and education should also focus on the actual cost of desalinated water, even where it is subsidized by government so that consumers have a realistic idea of the cost of water. This should be a core part of water conservation education. As the demand for the resource increases, unless technologies evolve to the point where the cost of production drops, governments may find it difficult to maintain the subsidies and the public would need to be suitably prepared for any increase in tariff rates. In countries where rainfall is more reliable, other augmentation options such as rainwater harvesting can be encouraged at the policy level as in Antigua and Barbuda, so that the demand from the municipal supply is decreased and allow for a reduction in government subsidies for desalinated water but resulting in little impact on the cost to consumers. As in Barbados, countries should also approach water management holistically with emphasis not just on increasing the output to the distribution system, but also maintaining the system to reduce unaccounted for water. The increased use of desalination in the Caribbean appears to be inevitable. The only question surrounds the extent to which it will be applied as a water augmentation option, or alternative to other augmentation options. Therefore efforts should be made to manage the implementation and the impacts that it could have in each country. The greatest consideration so far is the disposal of the brine and the return on investment. Once


policies have been put in place to address these and the concerns of all the stakeholders, the application of desalination will most likely result in positive impacts on the country, as physical development and expansion of services is contingent upon water availability. Development is inextricably linked to water availability.


Sources of Information

Antigua/Barbuda • John Bradshaw, Water Manager, Antigua Public Utilities Authority • Daniel Aburime, Production Engineer, Crabbs Power & Desalination Plant, APUA • Rodney Dickenson, Plant Manager, Enerserve/Veolia Water, Crabbs • Thierry Le Cras, Enerserve/Veolia Water, Crabbs Bahamas • Dr. Richard Cant, Assistant General Manager, Water & Sewerage Corporation

Barbados • Dr. John Bwalya Mwansa, Project Manager, Barbados Water Resources Management

and Water Loss Studies, Barbados Water Authority • O. Carlyle Bourne, International Hydrological Programme Focal Point, Ministry of

Agriculture • Harriet Waldron, Ionics/GE Grenada • Lester Arnold, Operations Manager, NAWASA • Alphonsus Daniel, Consultant, Daniel and Daniel Consulting, Grenada Mexico • Manuel Fuentes, Water Quality and Treatment Coordinator, IMTA Trinidad & Tobago • John Thompson, The Desalination Company of Trinidad & Tobago (Desalcott), Point

Lisas • Claire McEwan, Desalcott, Point Lisas St. Lucia • Shanta King, Operations Manager, Water & Sewerage Company (WASCO)

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References

��Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and (Lima, Peru, 19-22 September 1995), OAS/UNEP

��The Cost of Environmental and Social Sustainability of Desalination; by Loizos

Loizides, Bsc, Msc, Dip. in Marine Pollution Chemistry

�� http://www.oas.org/osde/publications/Unit/oea59e/ch09.htm# �� http://www.guardian.co.tt/archives/2004-06-29/bussguardian3.html

�� http://www.ric.org.tt/home/news/ReviewOfStatusOfWASA.pdf �� Drought Hazard Assessment and Mapping for Antigua and Barbuda , Post-

Georges Disaster Mitigation Project in Antigua & Barbuda and St. Kitts & Nevis, April 2001

�� http://www.halcrowwaterservices.co.uk/pdf/The%20sea%20shall%20quench.pdf �� Introduction to Desalination Technologies, Hari J. Krishna, 2005 �� Lester H. Forde PhD; Water for the People, A Water Supply and Sanitation NGO;

Public-Private Cooperation in Water Supply provision: An Example From Trinidad and Tobago

��Environmental Impact Assessment for Desalination Plant at Point Lisas,

Ecoengineering consultants Limited, 23 November 1999

��Feasibility Study on the Establishment of a Desalination Plant in Barbados, William Ambrose Johnson, October 1996

�� http://countrystudies.us/caribbean-islands/109.htm

�� http://www.cia.gov/cia/publications/factbook/

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http://www.oas.org/osde/publications/Unit/oea59e/ch09.htm#

http://www.guardian.co.tt/archives/2004-06-29/bussguardian3.html

http://www.ric.org.tt/home/news/ReviewOfStatusOfWASA.pdf

http://www.halcrowwaterservices.co.uk/pdf/The%20sea%20shall%20quench.pdf

http://countrystudies.us/caribbean-islands/109.htm

http://www.cia.gov/cia/publications/factbook/


Acronyms & Technical Abbreviations

APUA Antigua Public Utilities Authority BWRO Brackish Water Reverse Osmosis BWA Barbados Water Authority CBWMP Caribbean Basin Water Management Programme CEHI Caribbean Environmental Health Institute CWWA Caribbean Water and Wastewater Association EIA Environmental Impact Assessment GOBSE Government of Barbados State of the Environment Report IMTA Mexican Institute of Water Technology MSFD Multi-Stage Flash Distillation NAWASA National Water and Sewerage Authority RO Reverse Osmosis SIDS Small Island Developing States UNESCO United Nations Educational, Scientific and Cultural Organization WSC Water and Sewerage Corporation WASA Water and Sewerage Authority WASCO Water and Sewerage Corporation WHO World Health Organisation WRMWLS Water Resources Management and Water Loss Studies gpd gallons per day imgd millions of imperial gallons per day km2 square kilometers kwh/d kilowatt hours per day l/d litres per day mgd millions of gallons per day m3/d cubic metres per day mg/l milligrams per litre ppm part per million


Appendix 1 Desalination by Reverse Osmosis

Desalination is essentially the process by which water is pressurized through a semi-permeable membrane to remove various minerals, salts, ions and microorganisms in order to make it potable and suitable for a number of other functions that require high quality water. Water is said to have undergone this process when the salt and ion content is reduced to less than 1,000 mg/l. The most popular commercial method of desalination in the Caribbean is Reverse Osmosis. This process involves three water streams: feed water which is the source water used for the process; product water or permeate, which is the desalinated water intended for use; and reject water, also called brine or concentrate, which is the waste water from the process. The feed water can be seawater or brackish water. Because of the lower salt content of brackish water, it takes less energy to remove the salts from this source and the salinity of the brine also results in potentially less impact on the receiving body, if that body is the ocean. The cost of desalinated water is therefore influenced by the amount of energy consumed in the process, which is in turn dependant on the concentration of the seawater, the operating pressure and the energy recovery system that is used. New plants need about 3.5-5 kWh per cubic metre of potable water. A simple diagrammatic representation of the process of Reverse Osmosis is captured below:

Source: O.K. Buros, et. Al., The USAID Desalination Manual, Englewood, N.J., U.S.A., IDEA Publications


The following illustrates the process by which water is separated over the membranes:

Reverse Osmosis Module The options for the disposal of the brine can include the disposal into deep saline aquifers or surface waters, which have a higher salt content. In some cases, it can be diluted with treated effluent and reused for irrigation of golf courses. The challenges associated with this system, and which are characteristic of desalination plants in general are:

��The dependence on energy ��The cost of energy ��The safe disposal of the brine ��The potential impact of poor weather on the feed water quality

The benefits include:

��The relatively short time within which these packaged systems can be erected and operationalized

��The relative ease with which plants can be expanded ��Reliability of these systems once they are properly maintained ��The reliability of source water, particularly seawater, compared to traditional

sources such as surface and ground water ��Provision of water in countries with no other water options such as small islands

with no surface or groundwater and no reliable rainfall, such as some of the islands and cays of the Bahamas.

In the Caribbean, reverse osmosis plants are currently more popular than thermal distillation plants and they compare favourably because:

��The overall energy consumption is lower than that of MSFD (about one half to one third depending on the technology). Lower energy consumption means fewer atmospheric emissions from fuel combustion.

��The temperature increase of the water is negligible. There are no thermal outfall problems. Distillation plants discharge the brine with a temperature of about 10 to 15°C above the seawater temperature


��High recovery rate of freshwater (30% – 70%) from seawater compared to thermal distillation (10%)

The disadvantages compared with thermal distillation includes:

��RO plants produce much more solid waste than thermal plants. ��There are no acceptable solutions for the disposal or reuse of the membrane

systems. ��The higher recovery rate means that a more concentrated brine is produced, (13. –

1.7 times more concentrated than the raw salinity), which can have greater impact on the receiving body or which requires more treatment before discharge


Source: http://www.unep.or.jp/ietc/Publications/TechPublications/TechPub-

Appendix 2

Desalination by Multi-Stage Flash Distillation

Distillation as a desalination process involves heating the influent saltwater until it is vaporized, and thus separated from its other constituent elements, before being cooled to produce freshwater. One of the methods by which this can be carried out commercially involves a type of thermal technology called Multi-Stage Flash Distillation.

Seawater is heated in a brine heater along a bank of tubes that is heated by condensed steam from within. The heated seawater then flows into another chamber called a stage where the pressure is modified to facilitate immediate boiling of the water. This results in the “flashing” of the heated seawater into steam. Typically, only a small percentage of the seawater making it to this chamber is converted to desalinated water. In some systems, the seawater can be passed through a number of stages with increasingly lower pressure, so that the water is boiled repeatedly without increasing the temperature. An MSFD plant can have anywhere from 4 to 40 stages. The water vapour is cooled to produce the desalinated water on tubes of heat exchangers within each stage. The cooling effect is facilitated by the incoming feed water and this has the benefit of also reducing the heat required to increase the temperature of this feed water entering the brine heater. The top feed temperatures of the process is normally between 90º – 120º C. Temperatures above 120º C can increase the efficiency of the plant, but can also lead to scaling and corrosion of the metal surfaces.

Multi Stage Flash Distillation Process

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http://www.unep.or.jp/ietc/Publications/TechPublications/TechPub-THE


The costs associated with this type of distillation process is heavily dependent on the thermal energy consumed in heating up the feed water, the electrical energy for other mechanical functions and the technical specifications and size of the system. To produce one cubic metre of potable water 12-25 kWh are needed. If the thermal energy can be recovered from the cooling stream from a power plant or if heat from the sun can be harnessed for the process, the costs can be dramatically decreased. A drawback of MSFD and other thermal distillation technologies is the discharge of corrosion products including: copper, nickel, iron, chromium, zinc and other heavy metals, depending on the alloys used in the physical structures of the plant.


Appendix 3

Multi Effect Distillation (MED)

Multi Effect Distillation

This type of distillation utilizes thermal technology. The evaporation processes is based on the cycle of latent heat when generating steam, usually used in combination with power stations. Each “effect” is a chamber where feed water is passed through at successively lower pressures. As the pressure increases, the temperature required to boil the water is decreased, so that the heat from one effect, can be used to heat the water in the next effect, which has a higher pressure. The performance ratio increases with the number of effects in the system. Heat exchanger tubes are found in each effect where the vaporized water is condensed. The MED plants work at a lower temperature (70°C) compared to as MSFD plants (90°C- 120°C).

Multiple Effect Distillation Process

Source: http://cape.uwaterloo.ca/che100projects/sea/med.html

http://cape.uwaterloo.ca/che100projects/sea/med.html



Appendix 4

Vapor Compression Distillation (VCD) Vapor Compression Distillation This method of thermal desalination is often used with MED or MSFD, but can be used on its own. It utilizes compressed vapor, as the name suggests, rather than heat exchange from steam produced in a boiler, for the evaporation of the feed water. The feed water is present in thin films on the inside of tubes in the evaporation chamber and the heat from the condensation of the compressed water vapor is used to cause evaporation of the feed water.

Vapor Compression Distillation Process �

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Source: http://cape.uwaterloo.ca/che100projects/sea/med.html�

http://cape.uwaterloo.ca/che100projects/sea/med.html

Documents

unesdoc.unesco.orgunesdoc.unesco.org/images/0022/002281/228110e.pdf · CEHI also wishes to thank the individuals and Water Utility companies, desalination companies and private operators